Timing of anesthetic emergence and early postoperative recovery in older adults undergoing thoracic surgery: a retrospective cohort study

BACKGROUND: Older adults are at heightened risk of adverse early postoperative outcomes, yet whether the time of day at which patients emerge from anesthesia influences these outcomes remains unclear. We therefore examined the association between late-day anesthetic emergence and early postoperative outcomes after thoracic surgery in older adults. METHODS: We conducted a retrospective cohort study of 8,118 patients aged 65-90 year undergoing elective non-cardiac thoracic surgery. Patients were classified into the daytime group (08:00-16:00) or late-day group (16:00-24:00) according to the start time recorded in standardized anesthetic emergence documentation. The primary outcome was emergence delirium during PACU stay. Secondary outcomes included prolonged PACU stay (≥ 90 min), serious PACU adverse events (unplanned ICU admission, reintubation, or extubation failure), and post-extubation arterial blood gas parameters. Inverse probability of treatment weighting based on propensity scores was used to estimate adjusted associations. RESULTS: Among included patients, 4,816 (59.3%) were classified into the daytime group and 3,302 (40.7%) into the late-day group. The late-day group had higher odds of emergence delirium (15.7% vs. 13.5%; adjusted odds ratio (aOR) 1.18, 95% confidence interval (CI) 1.08-1.29), prolonged PACU stay (15.8% vs. 14.2%; aOR 1.12, 95% CI 1.02-1.22), and serious PACU adverse events (0.5% vs. 0.2%; aOR 2.67, 95% CI 1.52-4.97). Small but statistically significant differences in post-extubation arterial blood gas parameters were also observed, with higher PaCO₂ and lower PaO₂ in the late-day group. Supplementary analyses indicated that the elevated delirium risk was concentrated within the 16:00-20:00 interval. Findings were consistent across prespecified subgroup and sensitivity analyses. CONCLUSIONS: In older adults undergoing thoracic surgery, late-day anesthetic emergence was associated with modestly higher odds of emergence delirium, prolonged PACU stay, and serious PACU adverse events. These findings suggest that anesthetic emergence timing may be a relevant consideration in perioperative recovery planning and PACU management.